Ethylene elastomer compounds having good processability and ageing properties

ABSTRACT

Compounds having improved properties of processability and elasticity after heat aging for molded and extruded rubber parts can be prepared by utilizing improved processability EPM and/or EPDM rubber with effective amounts of carbon black prepared in a manner such that it has an average particle size of from 70 to 120 nanometers, a particle size distribution including from 40 to 225 nanometers sized particles, a surface area of 16 to 30 m 2  /g as measured by the BET adsorption, and a structure of 90 to 125 as measured by DBP absorption. The EPM and EPDM rubber useful in accordance with the invention will include those multimodal polymer blends that comprise at least two fractions having different molecular weight and, optionally, monomer composition. The invention compounds find particular use in automotive industry parts requiring high temperature tolerance, such as coolant hoses.

TECHNICAL FIELD

This invention relates to vulcanizable olefinic elastomers and tospecific applications of compositions comprising them. In particular theinvention relates to elastomeric compositions having improved propertiesof processability, compound strength and elasticity before and aftervulcanization, and long-term heat resistance of the vulcanizedcompounds.

BACKGROUND ART

The use of vulcanized rubber in many applications is well documented inpublic literature. Due to the inherent properties of the essentiallyelastic olefinic polymers many enduse applications require the use ofmodifying and reinforcing materials to bring out desired properties.Thus a rubber compounder will strive to arrive at a formulation thatwill give the best balance of processing behaviour, vulcanization (cure)rate, vulcanizate physical properties and cost. The olefin-basedelastomers of this invention are well-known to be some of the cheapestpolymers currently available and yet still capable of achievingexcellent properties in many of the otherwise most adverse applications.

Olefinic rubbers find many uses in the automotive industry because oftheir relatively low cost and as well because of their properties withrespect to moldability and extrudability, or ability to be readilyshaped as desired, and their ability to withstand oxidative attack. Inparticular the rubber compounds based upon ethylene-propylene monomer("EPM") and ethylene-propylene-diene monomer ("EPDM") elastomericpolymers are playing an ever-expanding role both for underhood and bodysealing parts. In particular it is known that certain EPDM grades haveshown excellent promise as automotive coolant hose polymers and as sealsand gaskets for both the automotive and building industries where largetemperature extremes test the ability to maintain an elastic seal.

In these applications it is known that the preferred compounds cantypically have 120-170 parts per hundred parts rubber ("phr") ofindustry-used carbon blacks as reinforcing fillers that serve to bothstrengthen and further reduce the overall cost of the compounds. Thetypically used and recommended carbon blacks are those furnace blacksmeeting ASTM designations (ASTM D 1765-1979) and falling into thefollowing classes: N550 FEF, N650 GPF, N762 SRF and N683 APF. Amongthese, N650/683 and N762 are closely defined as standard blacks inISO/DIN 6809.

The usefulness of EPDM polymers in these compounds depends on the curerate and cure state as well as the ease of fabrication. Thus it is knownthat improved properties of faster cure and better processing propertiescan be achieved where the polymers have selected molecular weightdistribution ("MWD") and intermolecular compositional distribution.Means of preparing the preferred broad MWD polymers meeting thesecriteria are disclosed in the patent literature. Representative recentpatents addressing the preparation of such polymers are U.S. Pat. Nos.4,722,971, 4,789,714, 4,792,595, 4,874,820, and 5,013,801. Earlierpatents that similarly address the preparation of specially tailoredgrades of EPM and EPDM polymers include GB 1 339 061, U.S. Pat. No.3,468,979, U.S. Pat. No. 3,884,993, GB 1 543 821, and GB 2 023 443.

Several of the documents above disclose the use of specific carbon blackfillers. In U.S. Pat. No. 4,722,971 carbon black N650 is used in anamount of 140 phr. In U.S. Pat. No. 4,792,595 the use of 80 phr of "highabrasion furnace black" is disclosed. U.S. Pat. No. 3,884,993 teachesthat 10-200 phr of carbon black, as a conventional filler, can be usedwith improved processability rubber. GB 1 543 821 exemplifies the use of70 parts "FEF black". GB 2 032 443 teaches that up to 300% by weight offillers, including carbon black, can be used in improved processabilityrubbery copolymers and exemplifies the use of a carbon black SEAST H®(TOKAI Carbon Co., Japan) in the amount of 67 parts by weight.

Additionally, automotive hose compounds utilizing carbon blacks a) N650GPF-HS (115 parts) with N762 SRF-LM (115 parts) with 137.5 parts EPDMrubber blend of high and low MW commercial grades (VISTALON® 3777 andVISTALON® 7000) and b) N550 FEF (110 phr) with N762 SRF-LM (50 phr) withimproved processing VISTALON® 7500 EPDM rubber are recommended in theVISTALON® Ethylene-Propylene Rubber User's Guide (Exxon Chemical Companybrochure 201-0888-01A, 1988) at page 10-7. It is stated that due toincreased underhood temperatures, it is appropriate to utilize selectedingredients in order to formulate EPM and EPDM compounds with high heatresistance.

INVENTION DISCLOSURE

It has been surprisingly found that particularly effective vulcanizableolefinic elastomer compounds can be prepared by carefully selecting boththe elastomeric polymer and the carbon black used as reinforcing filler.Accordingly compounds having optimal properties for molded and extrudedrubber parts can be prepared by utilizing improved processability EPMand EPDM rubber with effective amounts of carbon black prepared in amanner such that it has an average particle size of from above 70 to 120nanometers, a particle size distribution including from 40 to 225nanometers sized particles, and a surface area of 16 to 30 m² /g asmeasured by the BET analytical technique. The carbon black structure is90-125 ml/100 g as measured by DBP absorption. The EPM and EPDM rubberuseful in accordance with the invention will include those multimodalpolymer blends that comprise at least two fractions having differentmolecular weights and, optionally, monomer composition. A first fractionwill comprise between 70 and 95 wt. % of the total polymer content andwill have a Mooney viscosity (ML(1+8), 125° C.) between 20 and 80, anM_(w) /M_(n) between 1 and 8, ethylene content of 45 to 65 wt. %polymer, and a diene monomer content of 1 to 9 wt. % polymer. A secondfraction will comprise 5 to 30 wt. % of the total polymer and will havea Mooney viscosity (ML(1+8), 125° C.) between 200 and 70,000, an M_(w)/M_(n) between 1 and 8, ethylene content of 45 to 70 wt. % polymer, anda diene monomer content of 0 to 9 wt. % polymer. Additional fractionsmay be optionally included so long as the foregoing conditions are metand may be part of the first or second fractions where meeting thecriteria of those fractions, or may be totally different fractionspresent in amounts not sufficient to cause a significant deteriorationof the sought properties.

By combining a multimodal polymer blend as described with the specificcarbon black described, and with the traditional compoundingingredients, it has been discovered possible to produce novel compoundshaving significantly improved properties combining easier processing,vulcanized strength, and retained elasticity after heat aging, as hasbeen sought for the rapidly developing automotive industry with itsincreasingly higher temperature tolerance requirements.

BEST MODE AND EXAMPLES OF THE INVENTION

The "improved processability EPM and/or EPDM rubber" of this inventionis defined for the purpose of this description, and for the claims, asthose vulcanizable elastomeric ethylene-containing polymers (1) formedfrom C₃ -C₁₆ alpha-olefins and, optionally, co-polymerizablenon-conjugated dienes, and (2) prepared or blended so as to have themultimodal characteristics providing the ease of processing sought. Thepreferred alpha-olefins are typically C₃ -C₆ alphaolefins and the mostpreferred are propylene, butene-1 and hexene-1. The non-conjugateddienes are any of those known in the art to be capable of Ziegler-Nattacoordination polymerization with the alpha-olefins. The typicallypreferred dienes are the bridged ring dienes described in U.S. Pat. No.4,722,971, particularly 5-ethylidene-2-norbornene, methylene norbornene,and vinylidene-norbornene. A fuller listing of suitable dienes andalphaolefins appears in U.S. Pat. No. 5,013,801. Both U.S. patents areincorporated by reference for purposes of U.S. patent practice.Additionally the use of the terms copolymer and terpolymers is to beinterpreted in their generic sense as including tetrapolymers,pentapolymers, etc. Thus one or more alpha-olefins and/or one or moredienes may be copolymerized with ethylene to form the vulcanizableelastomeric polymers of the invention.

The improved processability EPM and/or EPDM rubber of this invention isprepared or blended so as to have the multimodal characteristicsproviding ease of processing as is described in the background artpatent documents. For example, these elastomeric polymers formed byZiegler-Natta coordination polymerization are physically blended, areprepared utilizing catalysts systems selected for their ability to formbroad MWD polymers, are prepared in multiple reactors, or are preparedin tubular reactors with multiple inlet ports for monomer and catalystsinjection. Such methods are well-documented in U.S. Pat. Nos. 4,722,971,4,786,697, 4,789,714, 4,792,595, 4,874,820, 5,013,801, 3,468,979, and3,884,993. All of which are incorporated by reference for purposes ofU.S. patent practice. GB 1 339 061, GB 1 543 821 , and GB 2 023 443provide additional teaching of easy processing rubbers. U.S. equivalents4,259,468 and 4,078,131 are also incorporated by reference for U.S.patent practice purposes.

The relationship of polydispersity (molecular weight distribution,"MWD") to processing characteristics has been addressed in publicliterature for EPDM-comprising compositions. Thus it is known that theexistence of high molecular weight (MW) fractions in EPDM compositionshave important impacts on process rheology. The existence of such highends can be characterized by the ratio of Z average molecular weight toweight average (M_(z) /M_(w)) with M_(z) /M_(w) preferably being between5 to 10, see "Designing EPDM for Production Efficiency" by G. Stella andN. P. Cheremisinoff, Polymer Plastic Technology and Engineering 28, No.2, pages 185-199 (1989). EPDM polymers having M_(z) /M_(w) below about 5are said to have insufficient high MW fraction to achieve bestprocessing results.

For relatively recent reviews of general methods for preparing EPM andor EPDM rubber, including catalysts, monomers, reaction conditions,etc., reference may be made to "Elastomers, Synthetic(Ethylene-Propylene)", by E. L. Borg in Encyclopedia of ChemicalTechnology, 3d. Ed., V.8 pp. 492-500 (Kirk-Othmer) and"Ethylene-Propylene Elastomers", by G. VerStrate in Encyclopedia ofPolymer Science and Engineering, 2d. Ed., V. 6 pp. 522-564 (J. Wiley &Sons, 1986).

Additionally, it is known to incorporate "branch suppressors" duringEPDM polymerization to reduce branching caused by the presence ofresidual sites of ethylenic unsaturation on each of the dienes. It isknown in the art that certain Lewis bases, e.g., NH₃, are effective asbranch suppressors. Additionally, certain alkoxy silanes, e.g., methylsilicate, ethyl silicate, etc., are known to act as effective branchsuppressors without reducing catalyst efficiency or reactivity. Thesebranch suppressors are added in known amounts and in accordance with theknown procedures.

The improved processability EPM and/or EPDM rubber useful in accordancewith the invention will include those multimodal polymer blends thatcomprise at least two fractions having different molecular weight and,optionally, monomer composition. A first fraction will comprise between70 and 95 wt. %, preferably 80 to 93 wt. %, of the total polymer contentand will have a Mooney viscosity (ML(1+8), 125° C.) between 20 and 80,preferably between 30 and 70; an M_(w) /M_(n) between 1 and 8,preferably 1.1 to 4.5; ethylene content of 45 to 65 wt. % polymer,preferably 50 to 60 wt. %; and, a diene monomer content of 1 to 9 wt. %polymer, preferably 2 to 7 wt. %. A second fraction, different from thefirst fraction, will comprise 5 to 30 wt. % of the total polymer,preferably 7 to 20 wt. %, and will have a Mooney viscosity (ML(1+8),125° C.) between 200 and 70,000, preferably between 500 and 10,000; anM_(w) /M_(n) between 1 and 8, preferably 1.1 to 4.5; ethylene content of45 to 70 wt. % polymer, preferably 50 to 65 wt. %; and a diene monomercontent of 0 to 9 wt. % polymer, preferably of 1 to 7 wt. %. In aparticularly preferred embodiment both first and second fractions willhave respectively an M_(w) /M_(n) of 1.2 to 3.5. So long as themolecular weight (represented by Mooney viscosity) of each fraction isas described, the monomer intermolecular composition distribution may bethe same or different for the two fractions. Thus the skewed ethyleneand diene contents disclosed in some of the background art patentdocuments, e.g., U.S. Pat. No. 4,722,971, represent alternativeembodiments of this invention.

Vulcanization, or curing by means of cross-linking a significant portionof the elastomeric polymers of the invention, is accomplished byconventionally known means. Curatives useful for the soughtcross-linking include peroxides, sulphur, sulphur donors, phenolicresins and brominated phenolic resins. Particularly preferred curativesare the peroxides for reasons of improved stability of the cross-linknetwork at high temperatures. The peroxide curatives will includemonovalent peroxides such as dibenzoyl peroxides, benzoylalkylperoxides, alkoylalkyl peroxides, dialkoyl peroxides, dibenzylperoxides, alkylbenzyl peroxides, dialkyl peroxides and their equivalentdivalent peroxides. For additional description see "PolyolefinElastomers of Ethylene and Propylene", F. P. Baldwin and G. VerStrate,Rubber Chemistry and Technology, 45, 709 (1972).

Mixing prior to vulcanization is typically accomplished by either thesingle or multi-step methods practiced in the relevant industries. Inthe single-step method the polymer(s), carbon black filler, conventionaladditives and modifiers, and curatives (last) are blended attemperatures as high as possible to facilitate the blending, but belowthe activation temperature of the curative. For example, blending isaccomplished below the decomposition temperature of the peroxy curativewhen such is used (typically at 100° C. whenbis(t-butylperoxyy-isopropyl) benzene is used). In the multi-stepmethod, the blending of all ingredients other than the curative isaccomplished in one or more steps at higher temperatures, e.g., 140° C.,and the blend is subsequently cooled before addition of the curative.Internal mixers such as those with tangential or intermeshing rotors,e.g. a Banbury, are typically used for the single-step method or theinitial mixing steps of the multi-step method. The necessary cooling istypically done on an open mill with subsequent addition and blending ofthe curative on the mill, or in a Banbury or other internal mixer. Thethus compounded olefinic elastomer blend is shaped by molding orextrusion and typically raised to a temperature of 150° C. to 240° C.The heat activates the cross-linking reaction and results in thevulcanization of the shaped compound. Any of the known methods forshaping rubber parts by molding or extrusion, and vulcanizing, will beuseful in accordance with the invention. For further information seeRubber Technology Handbook, Hoffman (Hansen, 1989).

Carbon black used in the rubber industry currently are classified intofive different types according to the method of manufacture. Thus theprevalent type is furnace black with all of channel black, lampblack,acetylene black and thermal black being much less prevalent. Each typegenerally meets the following characterization. The individual carbonblack particles approximate to spheres in shape but exist in chains orclusters, referred to as aggregates. The aggregates in turn tend tocluster in agglomerates which are believed to break up on mixing withrubber. Aggregates however tend to escape break-up and in essencerepresent the units of carbon black found within the vulcanizate. Thetype of aggregate indicates the "structure" of the black and representsthe ratio of the surface area of the black exposed to the rubbermolecules to that hidden from the rubber inside pores or channels toosmall for the rubber molecules to penetrate. The higher the structure,the greater the number of particles per aggregate. Carbon blacks thuscan be conveniently characterized accordingly by basic sphere size,structure (aggregate size and shape), and surface areas. Means ofanalyzing carbon black can be found in Analysis of Rubber andRubber-like Polymers, Chapter 11, pages 220-238 (Applied SciencePublishers, 3rd Ed., 1983).

The lampblack of this invention is one having a low surface area (highaverage particle size), broad particle size distribution, and a highstructure. Thus the following characteristics describe the best-modeselection as currently known for the invention: (a) an average particlesize of 70-120, preferably 80-120, and most preferably 100-120; (b) abroad particle size distribution including particles of at least 40nanometers and particles of 225 nanometers,, preferably 50 to 200; and(c) a surface area of 16 to 30 m² /g, preferably 18 to 28, as measuredby BET analysis or 20-40 mg/g as measured by iodine adsorption.Structure should be, as measured by DBP absorption in accordance withISO 4656-1978 (ml/100 gm), 90-125, preferably 95-108. Carbon blackmeeting these criteria is currently available commercially under thetradename DUREX-O® from Degussa AG, Germany. The invention carbon blackis typically used within conventionally known amounts, preferably forelasticity retention from 65 up to and including 150 phr, morepreferably between 70 and 115 phr. The carbon black to be used inaccordance with the invention can be produced by the lampblack, alsoknown as flameblack, method. Though such blacks are some of the oldesttypes known, the lampblack are not assigned ASTM designations, probablydue to the current lack of use of them in large quantities. The methodsof manufacture are well known and consist generally of burning acombustible liquid, extracting the smoke or fumes via a tube or chimney,and separating the carbon black via cyclone or filter separators. Thecombustible liquid is typically a fuel oil.

Conventional additives and modifiers typically include the followingwhich are generally known to be useful in the indicated amounts. Thesecompositions and amounts are to be considered illustrative andrepresentative only, the list is not intended to represent a limitationon the invention as described.

    ______________________________________                                        Function    Additive/Modifier Amounts (phr)                                   ______________________________________                                        Plasticizers/process                                                                      paraffinic oils   25-70                                           oils                                                                          Processing aids                                                                           polyethylene waxes                                                                               2-10                                                       stearic acid                                                                  zinc stearate                                                                 calcium stearate                                                  Stabilizers aromatic aimines  0.5-3.5                                                     hindered phenols or polymeric                                                 dihydroquinolines                                                 Vulcanization                                                                             triallylcyanurate 0.5-3.0                                         activators  isocyanurate                                                                  trialkyl phosphate                                                            trialkylmellitate                                                             dialkylpthalate                                                               m-phenylene-bis-maleimide                                                     ethyleneglycol-dimethylacrylate                                               trimethylolpropane-                                                           trimethylacrylate                                                             1,3 butyleneglycol-                                                           dimethylacrylate                                                  Curatives   peroxides, sulphur, etc.                                                                        1.5-10                                          White fillers                                                                             calcium carbonate  5-50                                                       calcined clay and silica,                                                     titanium dioxide etc.                                             ______________________________________                                    

Typical industrial applications of the compounds of the inventioninclude the following: all parts which are related to liquid transfer orsealing, e.g., coolant hoses, spouted hose splicing compounds, radiatorseals, brake hose tubes, hydraulic brake hose covers, brake cups; allparts related to transport of bulk materials such as minerals (coal,rock, etc.), e.g., conveyor belts; and, all parts related to hightemperature service in the automotive industry, e.g., engine mounts,exhaust pipe hangers, headlamp gaskets, V-belts or in the buildingindustry, e.g., profiles and sealing gaskets. The following examples arepresented to illustrate the foregoing discussion. All parts, proportionsand percentages are by weight unless otherwise indicated. Although theexamples may be directed to certain embodiments of the presentinvention, they are not to be viewed as limiting the invention in anyspecific respect.

EXAMPLE 1

The EPDM polymers in this example were commercially available productscharacterized as shown in Table 1. The comparison product was VISTALON®7509 (Exxon Chemical CO., Houston, Tex., USA) having an M_(z) /M_(w)indicative of essentially single mode MWD. The example of the inventionutilized VISTALON® 7500 (Exxon Chemical Int. Marketing B. V., Kraainem,Belgium) which has an M_(z) /M_(w) indicative of a high molecular weightfraction and is sold as a tailored grade having narrow MWD, and high andlow ends for good processing.

The comparison V7509 polymer and V7500 are described in Table I. Thecompound properties are described in Table II.

                  TABLE I                                                         ______________________________________                                        Polymers characteristics                                                      Polymer                                                                       Characteristics V 7509 Comparison                                                                          V 7500                                           ______________________________________                                        Mooney viscosity                                                                              70           82                                               ML (1 + 8), 125° C.                                                    Ethylene content                                                                              50           50                                               wt %                                                                          ENB content, wt %                                                                             2.6-3.0        3.5                                            (5-ethylidene-2-                                                              norbomene)                                                                    MWD M.sub.w /M.sub.n                                                                            2.5         6                                               M.sub.z /M.sub.w                                                              ______________________________________                                    

The principal process benefit of using the polymer of the invention isthe decrease in bulk viscosity of the compound as clearly shown by thelower compound Mooney viscosity measurement done at 100° C., compared tothe V7509 comparison (See Table II).

                  TABLE lI                                                        ______________________________________                                        Compound properties                                                           Polymers             V 7509                                                   Characteristics      Comparison                                                                              V 7500                                         ______________________________________                                        Mooney viscosity, ML (1 + 4) at 100° C.                                                     103       82                                             (ISO 289)                                                                     Physical properties after vulcanisation                                       at 180° C. for 20 min.-100% Modulus,                                                        2.5       2.6                                            MPa                  550       500                                            Elongation at break, MPa (ISO 37-1977)                                        Compression set, % after vulcanisation at                                                          72        68                                             180° C. for 20 min.-22 h at 160° C. + 3 h                       at 25° C. (VW P3307)                                                   Physical properties after air ageing, 96 h                                    at 160° C. (ISO 37-1977)                                               100% Modulus, MPa    3.1       3.2                                            Elongation at break, MPa                                                                           380       360                                            Physical properties after oil ageing, 22 h                                    at 100° C. (ISO 37-1977)                                               100% Modulus; MPa    2.5       3.0                                            Elongation at break, MPa                                                                           345       350                                            ______________________________________                                        Formulation:                                                                  Polymer        100 pbw   V7509 and V7500                                      Durex-O ®  110 phr   carbon black filler                                  (Degussa A.G., Germany)                                                       Flexon 815 ®                                                                              45 phr   paraffinic oil                                       (ESSO S.A.F., France)                                                         Flectol H ®                                                                               1 phr    polymeric (2,2,4-trimethyl-                          (Monsanto S.A., Belgium) 1,2-dihydroquinoline),                                                        stabilizer                                           EDMA ®      0.5 phr  ethylene/glycol                                      (Lehman + Voss and Co.,  dimethylacrylate,                                    Germany)                 activator                                            Perkadox ® 1440                                                                           7 phr    bis(t-butylperoxy-isopropyl)                         (Akzo B.V., Holland)     benzene                                              ______________________________________                                    

EXAMPLE 2

In this example, the V7500 described in Table I was compounded with 3different types of carbon black: the flame-black which is the basis ofthe invention and two carbon blacks produced with a furnace process (FEFN-550 and SRF N-774). In the 3 cases, the carbon black levels wereadjusted to keep the compound hardness as constant as possible. FEFN-550 black has a larger surface area (smaller average particle size)than the flame black but an almost comparable structure (comparable DBPabsorption values) whereas the SRF N-774 has a comparable surface area(same average particle size) with a lower structure (Table III).

                  TABLE III                                                       ______________________________________                                        Carbon black characteristics                                                              Durex-O ®                                                                          FEF N-550 SRF N-774                                      ______________________________________                                        Surface area                                                                  Iodine adsorption, g/kg                                                                      28         44       25                                         Structure                                                                     DBP absorption, ml/100 gr                                                                   102        118       75                                         ______________________________________                                    

The properties of the compounds obtained with these 3 carbon blacks aredescribed in Table IV.

                  TABLE IV                                                        ______________________________________                                        Compound properties                                                                        Durex-O ®                                                                         FEF N-550 SRF N-774                                      ______________________________________                                        Hardness (AFTM P2240-86)                                                                     57        59        55                                         Mooney viscosity at 100° C.                                                           87        79        73                                         (ISO 37-1977)                                                                 Physical properties                                                           (ISO 37-1977) after                                                           vulcanisation at 180° C. for                                           20. min.-                                                                     100% Modulus, MPa                                                                            2.6       2.4       1.8                                        Elongation at break, MPa                                                                     500       320       345                                        Compression set, % after                                                                     68        68        74                                         vulcanisation at 180° C.                                               after 20 min-                                                                 22 h at 160° C. + 3 h at                                               25° C. (VW P 3307)                                                     Physical properties                                                           (ISO 37-1977) after air                                                       ageing, 96 h at 160° C.-                                               100% Modulus, MPa                                                                            3.2       3.3       3.0                                        Elongation at break, MPa                                                                     360       275       260                                        Physical properties                                                           (ISO 37-1977) after oil                                                       ageing, 22 h at 100° C.-                                               100% Modulus, MPa                                                                            3.0       3.3       2.2                                        Elongation at break, MPa                                                                     350       190       215                                        ______________________________________                                        Note:  Table IV compound formulation, as in Table II with the                        following carbon black loading:                                               FEF            100 phr                                                        SRF            130 phr                                                        Durex-O ®  110 phr                                             

Compared to the FEF N-550 compound, the Durex-O® compound shows improvedmodulus at 100% elongation and, elongation at break on the originalvulcanized samples as well as on the oil and air aged samples. Theimprovement observed with the Durex-O® compound is even more apparentwhen the comparison is done with the SRF N-774 compound.

Although the invention has been described with respect to particularmaterials, means and embodiments it is to be understood that theinvention is not limited to the particulars disclosed and extends to allequivalents within the scope of the claims.

The following is claimed:
 1. An elastomer compound wherein theimprovement comprises an elastomer selected from the group consisting ofEPM and EPDM elastomer and a carbon black said carbon black having (i)an average particle size of from 70 to 120 nanometers, (ii) a particlesize distribution including from 40 to 225 nanometers sized particles,(iii) a surface area of 16 to 30 m² /g as measured by BET adsorption,and (iv) a structure of 90-125 ml/100 g as measured by DBP absorption;wherein said elastomer includes at least two fractions having differentmolecular weights; a) a first fraction constituting 70 to 95 weightpercent of the total elastomer content, having a Mooney viscosity(ML)(1+8), 1250° C.) between 20 and 80, M_(w) /M_(n) between 1 and 8, anethylene content of 45 to 65 weight percent, and a diene monomer contentof 1 to 9 weight percent; and b) a second fraction constituting 5 to 30weight percent of the total elastomer having a Mooney viscosity(ML)(1+8), 125° C. between 200 and 70,000 end M_(w) /M_(n) between 1 and8, an ethylene content of 45 to 75 weight percent, and a diene monomercontent of 0 to 9 weight percent.
 2. The compound according to claim 1wherein said first fraction a) has a Mooney viscosity (ML(1+8), 125° C.)between 30 and 70, M_(w) /M_(n) of 1.1 to 4.5, ethylene content of 50 to60 wt. % polymer, and diene monomer content of 2 to 7 wt. %; and, saidsecond fraction b) has a Mooney viscosity (ML(1+8), 125° C.) between 500and 10,000, an M_(w) /M_(n) between 1.1 and 4.5, and a diene monomercontent of 1 to7 wt.%.
 3. The compound according to claim 2 wherein bothof said first fraction a) and said second fraction b) have an M_(w)/M_(n) of 1.2 to 3.5.
 4. The compound according to claim 3 wherein saidcarbon black is selected from the group consisting of lampblack andflameblack.
 5. A shaped rubber product made from the vulcanizableolefinic elastomer compound of claim
 1. 6. The shaped rubber product ofclaim 5, wherein said shaped rubber product is used repeatedly intemperatures exceeding 125° C.
 7. The shaped rubber product of claim 6,wherein said shaped rubber product is selected from the group consistingof an automotive cooling hose, an automotive sealing gasket, anautomotive body seal, a building seal, a building profile and a gasketfor mechanical products.
 8. A vulcanizable olefinic elastomer compoundcomprising:a) at least two olefinic elastomers said olefinic elastomersincludingi) in the range of from 80 to 93 weight percent of a firstolefinic elastomer said first olefinic elastomer having in the range offrom 50 to 60 weight percent ethylene, in the range of from 2 to 7weight percent diene, said first olefinic elastomer having a ML(1+8)125°C. in the range of from 30 to 70, a M_(w) /M_(n) in the range of from1.1 to 4.5, wherein said diene is selected from the group consisting of5-ethylidene-2-norbornene, methylene norbornene, andvinylidene-norbornene; and ii) in the range of from 7 to 20 weightpercent of a second olefinic elastomer said second olefinic elastomerhaving in the range of from 50 to 65 weight percent ethylene, in therange of from 1 to 7 weight percent diene, said second olefinicelastomer having a ML(1+8)125° C. in the range of from 500 to 10,000, aM_(w) /M_(n) in the range of from 1.1 to 4.5, wherein said diene isselected from the group consisting of 5-ethylidene-2-norbornene,methylene norbornene, and vinylidene-norbornene; and b) a carbon black,said carbon black present in said vulcanizable olefinic elastomercompound in the range of from 70 to 115 parts per hundred partselastomer, said carbon black selected from the group consisting oflampblack and flameblack, wherein said carbon black has:i) an averageparticle size in the range of from 100 to 120 nanometers; ii) a particlesize distribution in the range of from 50 to 250 nanometers; iii) asurface area in the range of from 18 to 28 m² /g as measured by BETadsorption; and iv) a structure in the range of from about 95 to 108ml/100 g as measured by DBP absorption.